Unused Image Cleaner is a free WordPress plugin that finds Media Library images nothing uses, in minutes, even on sites with millions of database rows. It reads the database once, builds an index of every image reference, then checks each image in a single pass. Check results 10 at a time, look up any image with "Where is it used?", and move confirmed images to the Trash, where they can always be restored. No Pro version, no limits, and nothing leaves your site.